//生成随机的字母！

public static void testRandom2() throws Exception {
        Random random = new Random();
        for( int i = 0; i < 8; i ++) {
                int choice = random.nextInt(2) % 2 == 0 ? 65 : 97; // 取得大写还是小写
                System.out.println((char)(choice + random.nextInt(26)));
        }
}
 
public static void testRandom1() throws Exception {
        String s = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
        char[] c = s.toCharArray();
        Random random = new Random();
        for( int i = 0; i < 8; i ++) {
                System.out.println(c[random.nextInt(c.length)]);
        }
}


//生成固定长度的随机字符串(包含字母和数字)
public static String getCharacterAndNumber(int length)     
{     
    String val = "";     
             
    Random random = new Random();     
    for(int i = 0; i < length; i++)     
    {     
        String charOrNum = random.nextInt(2) % 2 == 0 ? "char" : "num"; // 输出字母还是数字     
                 
        if("char".equalsIgnoreCase(charOrNum)) // 字符串     
        {     
            int choice = random.nextInt(2) % 2 == 0 ? 65 : 97; //取得大写字母还是小写字母     
            val += (char) (choice + random.nextInt(26));     
        }     
        else if("num".equalsIgnoreCase(charOrNum)) // 数字     
        {     
            val += String.valueOf(random.nextInt(10));     
        }     
    }     
             
    return val;     
}